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Perception > Chemical senses > Flashcards

Chemical senses Flashcards

1
Q

why do we have senses

A

to depict the world around us
detect good and bad stimuli
evoke positive and negative responses to ensure our survival

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2
Q

what is the olfactory system

A

the system which determines our sense of smell

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3
Q

what is odour identification dependent on

A

the oderant - molecules the olfactory system can specifically recognise
single receptor tuned to small subset of orderants
the concentration - must be large enough in air to evoke a response

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4
Q

define transduction

A

neural activity that occurs when odour molecules activate receptors in the nose/mouth

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5
Q

what is the detection threshold for vanillin

A

0.000035 ppm

strong in small concentrations

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6
Q

wat is the detection threshold for methanol (ie antifreeze)

A

141 ppm

strong in high concentrations

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7
Q

define ‘Just Noticeable Difference’ (JND)

A

% concentration in air that needs to be changed by in order to recognise the odourant
can be as little as 5%

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8
Q

describe how no visual information can impact on the identification of odours

A

found to have generally poorer perfomance w/o visual info

identification seems to rely heavily on contextual cues ie smell flowers when in a garden

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9
Q

how does age influence odour identification

A

doty et al 1984
70yrs - drop off point in ability to smell odours
generally more likely in males than females

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10
Q

what is used to test smell identification abilities?

A

university of pennsylvania smell identification test (UPSIT)

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11
Q

how can smoking influence odour identification

A

frye et al 1990
smoking can be detrimental
strong association between years smoked and ability to detect different odours

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12
Q

how many types of olfactory receptors are there

A

350 types

10,000-20,000 of each type

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13
Q

how is the olfactory system laid out

A

olfactory bulb located above nasal passage
has cilia of olfactory receptor neurons which go into nasal passage
nasal passage lined with mucus to pick up odour molecules

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14
Q

what is the function on olfactory receptors

A

detect specific subtypes of odours

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15
Q

what are GPCRs

A

G protein coupled receptors - specific class of ORN predominant in the function of taste and smell

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16
Q

how do odours and receptors interact?

A

odour molecules dissolve into nasal mucosa
make contact with receptor
calcium and sodium enter receptor cells via ion channels
summation at axon hillock - determines ap to brain if threshold reached
signal sent to gloeruli in olfactory bulb which sends to higher cortical areas

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17
Q

describe malnic et al 1999

A 
receptors and oderants are specific
in mice
octanoic acid and noanoic acid activate receptors 1,18,19,41,46 and 51
BUT
octanoic also 79 and 83
noanoic also 83 and 86
- specific amount for a specific pattern
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18
Q

describe glomeruli in olfactory bulb

A

fletcher et al 1999
diff odours produce specific patterns of activation in glomeruli subsets
receptors of one type conerge at same point on glomeruli

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19
Q

how are odours synthesised in the cortex

A

olfactory mucosa > olfactory bulb piriform cortex orbitofrontal cortex

olfactory bulb entorhinal cortex

entorhinal cortex orbitofrontal cortex/hippocampus

olfactory bulb amygydala hypothallamus/piriform cortex/orbitofrontal cortex

orbitofrontal cortex>hypothallamus

COMPLEX

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20
Q

what does the piriform cortex consist of

A

the primary olfactory area and primary auditory cortex

dedicated to olfaction - direct info from olfactory bulb

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21
Q

describe the different parts of the piriform cortex

A

aterior - produce representations of the chemical structure of the odour molecule
peripheral - produce representations of odour as a whole

22
Q

describe the amgdalas role in olfaction

A

linked directly to olfactory bulb
activated by emotional stimuli - pleasant and unpleasant odours
sends signals to hypothallamus - invovled in instinctual behaviours ie hunger and smell of food

23
Q

describe the entorhinal cortexs role in olfaction

A

passes info to the hippocampus
invovled in storage and retrieval of long term memories
link smell to previous experiences

24
Q

describe the orbitofrontal cortexes role in olfaction

A

known as “secondary olfaction area”
recieveds info from amygdala, piriform cortex and entorhinal cortex
evaluates incoming stimuli as positive or negative

25
Q

describe the representation of odour in the piriform cortex

A

seltler and axel 2009 - activation becomes more spread out compared to order in olfactory bulb as neural activation becomes associated

26
Q

what types of taste sensations/tastants are there

A 
sweet
salty
umami (savoury)
bitter
sour
27
Q

what are tastants influenced by

A

onset/aftertaste
intensity
hedonics
loclisation

28
Q

define onset/aftertaste

A

how the taste unfolds over time

29
Q

define intensity of tastants

A

concentration of tastants

higher concentration = great receptivity of neurons

30
Q

define hedonics of tastants

A

if the taste is pleasant or unpleasant

31
Q

define the localisation of tastants

A

where the taste is sensed

32
Q

what tastants are hedonically pleasant

A

sweet
salty
umami
mild sour

33
Q

what tastants are hedonically unpleasant

A

strong sour

bitter

34
Q

describe the structure of the tongue

A

back of tongue - circumvilitate and foliates
filliform in mid tongue
fungiform in end of tongue

35
Q

describe a taste bud

A 
within the filli and fungiform
"fungiform papilla"
has receptors on hair
covered in tasre celles with taste pore similar to cilia
connected to nerve fibres
36
Q

describe tastant receptor sites

A

all sites specific to the tastant ie sour let in hydrogen, salt let in sodium

37
Q

what types of papillae are there

A

fungiform
foliate
circumvilliate
filiform

  • all contain tastebuds with certain taste cells that have receptors on the tip
38
Q

define a GPCR receptor

A

release ATP into tissue fluid when activated
atp attach to cranial nerve presynaptic cells
ie sweet, bitter, umami

39
Q

define a presynaptic receptor

A

passes info via serotonin to activate cranial nerve

ie salty, sour

40
Q

what receptors and tastants pair for sweet

A

TR2 & TR3

41
Q

what receptors and tastants pair for bitter

A

T2R1 & TR2

25-30 diff types as want to detect for toxicity

42
Q

what receptors and tastants are tere for umami

A

T1R2 & T1R3

43
Q

describe the connection between the mouth and the brain

A

faurion et al 1998
tongue>nucleas of salitary tracgt>thalamus>insula

insula>amygdala/orbitofrontal c/hypothallamus/anterior insula/frontal operalum/superior temp gyrus

44
Q

how is the amygdala, orbitofrontal c and hypothallamus linked to taste

A

amygdala - representation of emotion
orbitofrontal c - reward value of food
hypothallamus - represent hunger

45
Q

define flavour

A

the occurance which combines the taste in the mouth and the smell in the olfactory system

46
Q

how does flavour occur

A

localisation of flavour occurs in mouth by oral capture - odour through retronasal path into mouth

47
Q

how is flavour percieved in the nervous system

A

insula (taste) interacts with olfactory bulb, amygdala, orbitofrontal cortex and hypothallamus which are also involved in olfactory system

48
Q

what other factors also contribute to the perception of flavour

A

hunger/thirst
expectation
vision
audition

how it feels in the mouth..ie. texture, temperature, spice, cool, dry etc

49
Q

describe plassman et al 2008

A

marketing can influence the neural representation of experienced pleasantness
higher priced wine rated as increased pleasant and increased activity in orbitofrontal cortex

-same wine

50
Q

describe o’doherty et al 2008

A

increased satiety of food can reduce pleasantness and make aversive
ie satiation in banana makes aversive
satiation in vanilla makes less pleasant

51
Q

link between taste, olfaction and transduction

A

both molecules activate receptors in mouth and nose causing neural activity and therefore our percetion

Perception (11 decks)

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